Morphometric differentiation among haplochromine cichlid fish species of a satellite lake of Lake Victoria

Lake Victoria holds a young but species‐rich assemblage of cichlid fishes, which form a monophyletic assemblage with additional species from surrounding water bodies, termed the Lake Victoria superflock. Lake Victoria is surrounded by smaller lakes that are somewhat disconnected from the main lake. Lake Kanyaboli is such a small lake, having markedly reduced species diversity, in part comprised of Lake Victoria species and endemics. Here, we studied the modern haplochromine component of the cichlid fauna, represented by Lipochromis maxillaris, Astatotilapia nubila, Xystichromis phytophagus and Astatotilapia sp. ‘Bigeye’, as well as a number of unidentified modern haplochromine specimens. We used landmark‐based geometric morphometrics to study the degree of morphological divergence among those young entities. Twenty landmarks and 14 interlandmark distances were used for shape analysis. Multivariate analysis revealed significant differences between all four species, but principal component analysis and canonical variate analysis did not clearly discriminate between A. nubila and X. phytophagus, demonstrating great overall morphological similarity despite clear dietary differences. Besides coloration there was sexual dimorphism in body proportions, so that only male individuals were analysed further. In all four species, the observed similarities and differences in body shape conform to the type of ecological specialization of the fish. Most unidentified specimens overlapped the range of A. nubila and X. phytophagus, while the assignment test based on the canonical variate analysis suggested 70% of the three overlapping entities as separate units. To test their reproductive distinctness and to demonstrate potential hybridization, nuclear genetic data are needed. Zusammenfassung Der Victoriasee beherbergt einen Hunderte von Arten zählenden Artenschwarm aus Haplochromis‐artigen Buntbarschen, die mit weiteren Spezies aus umgebenden Gewässern einen monophyletischen ‘Super‐Schwarm’ bilden. Der Victoriasee ist umgeben von kleineren Seen, die nicht direkt mit ihm in Verbindung stehen. Der Kanyaboli‐see ist ein solcher kleiner Satellitensee, der, verglichen mit dem Hauptsee, eine beträchtlich geringere Anzahl an endemischen Arten vorweist. In dieser Studie wurden die vier bisher bekannten ‘modernen Haplochrominen’ vergleichend morphometrisch untersucht, repräsentiert durch Lipochromis maxillaris, Astatotilapia nubila, Xystichromis phytophagus und Astatotilapia sp. ‘B